1. Field of the Invention
Example embodiments of the present invention relate to a memory device and a method of manufacturing a memory device. More particularly, example embodiments of the present invention relate to an electrical-mechanical memory device including an electrode capable of bending in response to an applied voltage, and a method of manufacturing the memory device.
2. Description of the Related Art
Memory devices with large capacity are in demand in response to developments of mobile devices, multimedia devices, etc. A conventional memory device is fabricated using a metal oxide semiconductor field effect transistor (MOSFET). However, as a design rule of the memory device decreases to provide the memory device with large capacity, a short channel effect and increases of resistance and parasite capacitance may result in the conventional memory device. Also, the memory device having the MOSFET is conventionally provided on a single crystalline silicon semiconductor substrate so that several memory devices may not be properly stacked on the substrate.
Considering these drawbacks in the conventional device, a device has been developed instead of the conventional MOSFET. A micro electromechanical system (MEMS) and a nano electromechanical system (NEMS) are employed in manufacturing current semiconductor devices. For example, a memory device including carbon nanotubes is disclosed in U.S. Patent Application Publication No. 2004/0181630 or U.S. Patent Application Publication No. 2006/0128049. In the memory device according to the above U.S. Patent Application Publications, data may be stored or erased by contacting carbon nanotube fabrics with an upper electrode or a lower electrode.
In the conventional memory device, the data is stored by mechanically moving the carbon nanotube fabric toward the lower electrode or the upper electrode. Thus, various materials including semiconductor materials may be used for a substrate so that several memory devices may be easily stacked on the substrate and a capacity of the conventional memory device may be easily increased. However, the conventional memory device including the carbon nanotube fabric may also have some drawbacks.
For example, when the carbon nanotube fabric makes contact with the lower electrode, a high voltage is applied to the carbon nanotube fabric and the lower electrode so that the carbon nanotube fabric overcomes a tension of the carbon nanotube fabric supported by a nitride layer on an insulating interlayer. Thus, power consumption of the conventional memory device may greatly increase.
Further, van der Waals forces may markedly affect the carbon nanotube fabric and the lower electrode or the upper electrode when a distance between the lower electrode and the carbon nanotube or the upper electrode and the carbon nanotube fabric is maintained by a nano-scale. Accordingly, the lower electrode or the upper electrode of the conventional memory device may not be easily separated from the carbon nanotube fabric due to an attractive force caused by the van der Waals forces after the carbon nanotube fabric makes contact with the lower electrode or the upper electrode. Additionally, repeated bending of the carbon nanotube fabrics may degrade operation characteristics of the conventional memory device, so, repeatedly bending the carbon nanotube fabric may need to be avoided.
Moreover, the carbon nanotube fabrics may not easily move when dimensions of the carbon nanotube fabrics decrease. Although the dimensions of the carbon nanotube fabrics increases to move the carbon nanotube fabrics toward the lower electrode or the upper electrode, a size of a unit cell of the conventional memory device may not decrease to a desired level when the carbon nanotube fabrics have large dimensions.